It is well-established that adolescence is a time of dramatic neuromaturation, paralleled by improvements in cognition, social functioning, and emotional regulation. In addition, cross-sectional studies have demonstrated that rising gonadal hormone levels associated with puberty influence emotional and appetitive processing and limbic brain structure and functioning. Given the rise in psychopathology during adolescence, the hormonal activation of limbic brain regions during puberty, coupled with the immaturity of sexually dimorphic prefrontal regulatory systems, may contribute to heightened adolescent vulnerability for psychopathology in a sex- specific manner; however, little longitudinal work has been done to fully explore this notion. To that end, this study will longitudinally follow 120 healthy, 12-15-year-old male and female adolescents after one year with a rich, multimodal neuroimaging and behavioral characterization. This assessment will include functional neuroimaging during working memory and decision making, resting state functional neuroimaging, diffusion tensor imaging, neurocognitive assessment, mood/behavior/personality assessment, and serum hormone assays. Using a multi-modal longitudinal design, we aim to better understand sex-specific structural and functional neuromaturation of the brain during adolescence and to explore associations with gonadal hormones, cognition, and behavior. Increased understanding of these relationships may help to explain sex- specific vulnerability, better dissociate hormonally influenced developmental pathways from those that are not, elucidate individual characteristics conferring risk and resilience, and may ultimately permit the development of targeted treatment strategies aimed at reducing adolescent psychopathology.